Tool device, and method for drilling

ABSTRACT

A tool, a device, and a method for drilling capable of very easily forming a hole part in a drilled matter by extremely smoothly discharging chips produced at drilled positions so as to maintain an excellent drilling efficiency. By using a drilling tool having a shaft with a spiral groove part formed in the outer peripheral surface thereof and a bit fixed to the tip part of the shaft, the hole part is formed in a drilled matter by rotating the shaft.

TECHNICAL FIELD

[0001] The present invention relates to a tool, a device, and a methodfor drilling, for example, a concrete.

BACKGROUND ART

[0002] Recently, measures have been taken to prevent falling of walltiles from old buildings. In a method used for achieving such a purpose,for example, a hole is formed in a tile or tile joint to a depthreaching to a base concrete, and a resin is introduced through the holeso that the tile is fixed from the back.

[0003] In order to form a hole in a concrete, a hammer drill orvibrating drill which forms a hole in a drilled matter by rotating asuper-hard drill so as to generate vibration or apply impact force isconventionally used. However, the drilling operation using a hammerdrill or a vibration drill has a disadvantage in that a large mechanicalsound is generated and vibration or noise associated with the operationis transmitted to the entire building. Thus, not only are the neighborsdisturbed by the noise, but also falling of tiles is accelerated and thebuilding may be further damaged.

[0004] In order to solve the above problems, a drilling tool of smalldiameter (3-15 mm) having a disc shaped bit at the tip of a rod-shapedor cylindrical shaft, and a drilling device, such as a handheld drill,including a rotation-driving device which rotates and drives thedrilling tool around its axis may sometimes be used. As the bit of thedrilling device, one in which super-grains are dispersed in a binderphase or one which is formed using a super-hard alloy is employed. Sincethe bit is rotated at a high-speed while it is pressed against a drilledmatter so that a hole is formed with the generation of fine powderchips, the noise generated by the drilling device is less compared tothat generated by a hammer drill or a vibration drill, and it becomespossible to carry out the drilling operation without causing vibrationto the drilled matter.

[0005] In the above drilling device, although the chips are dischargedby passing through a space between the surface of the wall being formedand the bit or the shaft, the fine powder chips tend to stay in the holeand are hardly removed as the depth of the hole increases. For a casewhere a liquid is introduced into the hole to facilitate the dischargeof chips, it becomes difficult to smoothly supply and discharge theliquid for the same reason. If the chips remain at the bottom of thehole, the bit cannot reach the drilled matter and the drilling processcannot be performed. Also, when a hole is formed to a certain depth, nochips may be discharged and the bit cannot be advanced any further.Accordingly, it is difficult to form a deep hole of small diameter.

[0006] Moreover, the chips may stay not only at the tip of a blade(bottom of the hole) but also around the drilling tool (side surface ofthe hole), breaking the tool and decreasing the number of rationsthereof. This causes a decrease in drilling efficiency, and there is adanger that heat may be generated and a brazed chip may fall.

[0007] In order to smoothly discharge the chips at the drillingposition, if a shaft is made hollow and a core bit which drills whileforming a core center in the hole is used, it becomes possible todecrease the amount of chips generated. Also, it becomes possible todischarge the chips by introducing a fluid, such as water and a gas,from the outside to the drilling position through the hole.

[0008] However, in a conventional wet process in which chips aredischarged by supplying water, the operation place may be swamped by thewater or the dirty water containing fine power chips may be spattered,contaminating the surrounding environment. Thus, a cleaning device maybe needed in addition to the drilling device, and hence the use of theconventional process is not preferable.

[0009] Also, as for the above-mentioned drilling tool of a smalldiameter of 3-15 mm, for example, a large amount of chips is generatedrelative to a hole of small diameter since a core bit cannot be employedwith the drilling tool. Also, since the fluid used for discharging thechips can be supplied only through an opening of the drilled hole, it isextremely difficult to discharge the chips generated.

[0010] That is, in the conventional drilling device, it is difficult toform a deep hole of small diameter, and not only is the drillingefficiency reduced as the depth of the hole increases, but also a holehaving a desired depth may not be formed, depending on the diameter ofthe hole. Furthermore, since the above drilling device requires not onlythe drilling tool and the rotation-driving device but also a device forsupplying fluid, such as a compressor, there is a problem in that thescale of the overall device is large.

DISCLOSURE OF THE INVENTION

[0011] The present invention is achieved in consideration of theabove-mentioned problems, and an object of the present invention is tovery easily form a hole part in a drilled matter by extremely smoothlydischarging chips produced at drilled positions so as to maintain anexcellent drilling efficiency

[0012] In order to achieve the above object, the first embodiment of thepresent invention provides a drilling device for forming a hole in abrittle drilled matter from which powdery chips are generated,including: a tool having a shaft and a disc shape bit which is fixed toan end portion of the shaft; and a rotation driving device which rotatesand drives the tool, wherein a spiral groove part which extends to a tipof the bit is formed in an outer peripheral surface of the shaft of thetool, and the tool is rotated at a revolution number of 250 m/min ormore by the rotation driving device.

[0013] According to the above embodiment of the invention, the rotationof the bit makes a hole in a drilled matter, and the spiral groove partgenerates air flow in the hole due to a high-speed rotation of theshaft.

[0014] The second embodiment of the present invention provides adrilling device according to the first embodiment, wherein the spiralgroove part is provided so as to generate air flow from a tip side ofthe shaft to a rear end side along the groove part by the rotation ofthe tool due to obliquity of the spiral groove part extending towards arear side of a rotation direction by the rotation driving device andtowards a rear end side of the shaft.

[0015] According to the above embodiment of the invention, air flowwhich flows from the tip side to the rear end side of the tool isgenerated by the high-speed rotation of the shaft, and powdery chipspresent in the hole are discharged outside by the air flow. Accordingly,chips do not remain at a drilled portion to prevent the drillingoperation, and a deep hole of small diameter, which is difficult to formusing a conventional technique, can be readily formed. Also, since chipsare immediately discharged from the drilled portion as the drillingoperation proceeds, a device which supplies a fluid to a drilled portionto discharge chips or a structure for supplying a fluid to a drilledportion becomes unnecessary and a simplified and labor saving drillingdevice may be realized.

[0016] The third embodiment of the present invention provides a drillingdevice according to the first or second embodiment, wherein a hole whichpierces though the shaft to reach the tip of the bit is formed in thetool so that a vicinity of the bit communicates with air present at arear end side of the shaft.

[0017] According to the above embodiment of the invention, since airflow which flows in one direction is generated between the inner wall ofthe hole part and the shaft by the high-speed rotation of the shaftwhile another air flow which flows in the opposite direction isgenerated by providing a hole in the tool which makes a drilled portioncommunicate with air present outside the hole, the flow of air becomessmooth. For example, an intake flow is generated in the hole if adischarge flow is generated between the inner wall of the hole and theshaft due to the high-speed rotation of the shaft. Also, it becomespossible to supply a gas, such as air, liquid, such as water andalcohol, and mist, etc., through the hole, and hence not only chips areefficiently discharged but also the drilled portion can be cooled down.

[0018] The fourth embodiment of the present invention provides adrilling device according to the first embodiment, wherein the spiralgroove part is provided so as to generate air flow from a rear end ofthe tool to a tip side of the shaft along the groove part by therotation of the tool due to obliquity of the spiral groove partextending towards a rear side of a rotation direction by the rotationdriving device and towards a tip side of the shaft, and a hole whichpierces though the shaft to reach the tip of the bit is formed in thetool so that the tip side of the bit communicates with air present at arear end side of the shaft.

[0019] According to the above embodiment of the invention, since airflow which flows in one direction is generated between the inner wall ofthe hole and the shaft by the high-speed rotation of the shaft while adischarge flow is generated through a piercing hole formed in the toolwhich makes a drilled portion communicate with air present outside thehole, the flow of air becomes smooth. Also, it becomes possible to drilla drilled matter while discharging chips through the piercing hole.Accordingly, since the chips can be collected through the piercing hole,it becomes possible to carry out a drilling operation without scatteringthe chips.

[0020] The fifth embodiment of the present invention provides a drillingtool, including: a shaft and a disc shape bit fixed to an end portion ofthe shaft, wherein a spiral groove part which extends to a tip of thebit is formed in an outer peripheral surface of the shaft, and the toolis rotated at a revolution number of 250 m/min or more to form a holepart in a brittle drilled matter from which powdery chips are generated.

[0021] According to the above embodiment of the invention, the rotationof the bit makes a hole in a drilled matter, and the spiral groove partgenerates air flow in the hole due to a high-speed rotation of theshaft.

[0022] The sixth embodiment of the present invention provides drillingtool according to the fifth embodiment, wherein the spiral groove partis provided so as to generate air flow from a tip side of the shaft to arear end side along the groove part by the rotation of the tool due toobliquity of the spiral groove part extending towards a rear side of arotation direction and towards a rear end side of the shaft.

[0023] According to the above embodiment of the invention, it becomespossible to obtain a drilling tool which generates air flow flowing fromthe tip to the rear end of the tool by a high-speed rotation thereof.That is, since powdery chips in the hole can be discharged outside bythe air flow, and hence the chips do not remain at a drilled portion toprevent the drilling operation, a deep hole of small diameter, which isdifficult to form using a conventional technique, can be readily formed.

[0024] The seventh embodiment of the present invention provides adrilling tool according to the fifth or sixth embodiment, wherein a holewhich pierces though the shaft to reach the tip of the bit is formed sothat a vicinity of the bit communicates with air present at a rear endside of the shaft.

[0025] According to the above embodiment of the invention, since airflow which flows in one direction is generated between the inner wall ofthe hole and the shaft by the high-speed rotation of the shaft whileanother air flow which flows in the opposite direction is generated inthe piercing hole, it becomes possible to carry out a drilling operationwhile smoothly performing discharging and intaking of air. For example,if a discharge flow is generated between the inner wall of the hole andthe shaft by the high-speed rotation of the shaft, an intake flow isgenerated in the piercing hole and chips are smoothly discharged. Also,it becomes possible to supply a gas, such as air, liquid, such as waterand alcohol, and mist, etc., through the piercing hole, and hence notonly chips are efficiently discharged but also the drilled portion canbe cooled down.

[0026] The eighth embodiment of the present invention provides adrilling tool according to the fifth embodiment, wherein the spiralgroove part is provided so as to generate air flow from a rear end ofthe shaft to a tip side of the shaft along the groove part by therotation of the tool due to obliquity of the spiral groove partextending towards a rear side of a rotation direction and towards a tipside of the shaft, and a hole which penetrates though the shaft to reachthe tip of the bit is formed so that a vicinity of the bit communicateswith air present at a rear end side of the shaft.

[0027] According to the above embodiment of the invention, since intakeflow is generated between the inner wall of the hole and the shaftduring a drilling operation while a discharge flow is generated throughthe piercing hole by the high-speed rotation, it becomes possible tocarry out a drilling operation while discharging the chips through thepiercing hole. Accordingly, the chips can be collected through thepiercing hole, and it becomes possible to carry out a drilling operationwithout scattering the chips.

[0028] The ninth embodiment of the present invention provides a methodfor drilling a hole part in a brittle drilled matter from which powderychips are generated by rotating and driving a drilling tool in which abit is fixed to a tip of a shaft, the method including the step of:performing a drilling process while generating air flow which flows froma vicinity of the bit to air present at a rear end side of the shaft byutilizing a rotation of the drilling tool.

[0029] According to the above embodiment of the invention, since therotation of the bit forms a hole in a drilled matter and air flow isthereby generated in the hole, it becomes possible to supply liquid,such as water, to a drilled portion from outside of the hole or todischarge powdery chips to the outside of the hole part by using the airflow.

[0030] The tenth embodiment of the present invention provides a methodfor drilling according to the ninth embodiment, wherein the air flowgenerated by utilizing the rotation of the drilling tool is a dischargeflow which flows from a tip side to a rear end side along an outside ofthe drilling tool.

[0031] According to the above embodiment of the invention, since thedischarge flow is generated during the drilling operation, it becomespossible to discharge the chips to the outside of the hole part from thedrilling portion by using the discharge flow. Accordingly, it becomespossible to prevent the chips to remain at the drilling portion, whichmay make the drilling operation impossible, and to carry out a smoothdrilling operation.

[0032] The eleventh embodiment of the present invention provides amethod for drilling according to the ninth or tenth embodiment, furtherincluding the step of: generating another air flow which flows anopposite direction of the air flow generated by the rotation of thedrilling tool, so as to flow through a hole which penetrates through atip side to a rear end side of the drilling tool.

[0033] According to the above embodiment of the invention, since each ofthe air flow which is separated by the drilling tool is smoothly flowsin the opposite direction at the inner periphery side and the innerperiphery side of the drilling tool having the piercing hole, it becomespossible to more efficiently discharge the chips.

[0034] The twelfth embodiment of the present invention provides a methodfor drilling according to the ninth embodiment, wherein the air flowgenerated by utilizing the rotation of the drilling tool is an intakeflow which flows from a tip side to a rear end side along an outside ofthe drilling tool, and further including the step of: generating anotherair flow which flows in an opposite direction of the intake flow so asto flow through a hole which penetrates through a tip side to a rear endside of the drilling tool.

[0035] According to the above embodiment of the invention, it becomespossible to discharge the chips from the drilling portion to the outsideof the drilled matter via the piercing hole through which the dischargeflow flows.

BRIEF DESCRIPTION OF DRAWINGS

[0036]FIG. 1 is a diagram showing a side view of an entire drillingdevice according to an embodiment of the present invention.

[0037]FIG. 2 is a diagram showing main parts of a drilling toolaccording to an embodiment of the present invention.

[0038]FIG. 3 is a diagram showing a side view of an entire drillingdevice according to another embodiment of the present invention.

[0039]FIG. 4 is a graph showing drilling performance of drilling toolshaving various bit diameter according to the present invention incomparison with that of conventional drilling tools.

[0040]FIG. 5 is a graph showing drilling performance of drilling toolsaccording to the present invention in comparison with that ofconventional drilling tools at various drilling depths.

BEST MODE FOR CARRYING OUT THE INVENTION

[0041] Hereinafter, embodiments of the present invention will beexplained with reference to the accompanying drawings.

[0042] In FIGS. 1 and 2, the numeral 10 indicates a drilling device andthe numeral 20 indicates a direct motor (a rotation-driving device) ofthe drilling device 10 which rotates and drives a drilling tool 13 thatcontacts a drilled matter C. The drilling device 10 is a handheld drill10 that a user can hold by hand to perform a drilling operation, andincludes a handle portion 30 which is fixed to a housing 16 having thedirect motor 20 therein. The handheld drill 10 may be switching on andoff by a trigger 31 disposed at the handle portion 30.

[0043] The direct motor 20 includes a cylindrical rotor 17 disposed inthe housing 16 and a cylindrical stator 18 disposed around the rotor 17.A cylindrical rotary shaft 11 is press fitted into a penetration hole 17a which is formed at the center of the rotor 17. Both ends of the rotaryshaft 11 are rotatably supported by bearings 19 a and 19 b which aredisposed inside an upper wall portion 16 a and a lower wall portion 16b, respectively, of the housing 16. That is, the bearings 19 a and 19 bsupport the vicinity of the upper and lower end portion, respectively,of the rotary shaft 11 which is inserted through the center of the rotor17 so that they can receive force applied to the rotary shaft 11 and therotor 17, through which the rotary shaft 11 is penetrated, in a thrustdirection and in a radial direction. Also, an upper housing 21 whichaccommodates a rear end portion of the rotary shaft 11 is attached to arear end portion of the housing 16.

[0044] The numeral 25 indicates a brush portion which is disposed in acircumferential direction so as to contact the rotary shaft 11 at anupper side of the diagram in the housing 16 of the direct motor 20. Adriving current is supplied to the direct motor 20 from a power source(not shown in the diagram) which is incorporated in the handle portion30 via the brush portion 25. Note that although a brush motor is used asthe direct motor 20 according to this embodiment, it is possible to usea brushless motor instead.

[0045] The drilling tool 13 is detachably attached to an end portion ofthe rotary shaft 11 which is placed at the center of the direct motor20, via an adaptor 12. The drilling tool 13 which is directly coupledwith the rotary shaft 11 has a structure in which a bit 15 is fixed toan end portion of a shaft 14. Since a space is required between an innerwall of a hole part H and the shaft 14 in order to generate air flow,the shaft 14 is made of a rod type member having a smaller diameter thanthat of the bit 15, and a spiral groove part 14 a is formed around anouter circumferential surface thereof. It is preferable to form thespiral groove part 14 a in the same manner as a general twist drill interms of the number and the angle of torsion, etc., since air flow canbe efficiently generated.

[0046] Note that the drilling tool 13 shown in FIGS. 1 and 2 has thespiral groove part 14 a which extends towards a rear end side whenfacing a rear side of the rotation direction, i.e., the windingdirection of the right-hand thread, so that a discharge flow which flowsfrom the vicinity of the bit 15 towards the rear end side along theshaft 14 can be generated when the drilling tool 13 is rotated in theright direction. On the other hand, if a spiral groove part whichextends towards a rear end side when facing a front side of the rotationdirection, i.e., the winding direction of the left-hand thread, isformed and the shaft is rotated in the right hand side direction, itbecomes possible to generate an intake flow which flows towards an endportion side along the shaft.

[0047] The bit 15 may by a diamond bit in which diamond grains are boundusing a metal bond, electrodeposition bond, a resin bond, etc., as abinder material, and is formed into a disc shape having a notch portion15 a as shown in FIG. 2. The shaft 14 and the bit 15 are fixed withtheir circumferential positions being matched as shown in FIG. 2 so thata trough portion of the spiral groove part 14 a becomes continuous withthe notch portion 15 a in the axial direction.

[0048] Next, a drilling operation for a drilled matter C using thehandheld drill 10 having the above configuration will be explained. Notethat the handheld drill 10 is suitable for drilling a brittle matter,such as a concrete and a glass, from which powdery chips W will begenerated by the operation of the bit 15.

[0049] First, the handheld drill 10 is set for the drilled matter C sothat the axis of the rotary shaft 11 aligns with a predeterminedposition of the drilled matter C where a hole is to be formed. Then, thetrigger 31 is activated to supply electricity to a coil of the rotor 17(or the stator 18) via the brush portion 25 of the direct motor 20 sothat the rotor 17 is rotated at a high speed. While the rotor 17 isrotated at a high speed, the handheld drill 10 is moved forward in theaxial direction of the rotary shaft 11 to make the bit 15 contact withthe surface of the drilled matter C at a predetermined pressure. In thismanner, the face of the tip of the bit 15 drills the drilled matter Cwhile producing powdery chips W, and a hole part H of a sizecorresponding to the size of the bit 15 is formed in the drilled matterC.

[0050] When the handheld drill 10 is further moved forward and the shaft14 of the drilled tool 13 enters inside the cylindrical hole part H, airbetween the inside wall of the hole part H and the shaft 14 is moved ina direction indicated by arrows in FIG. 2 due to the high-speed rotationof the spiral groove part 14 a, and a strong discharge flow in abackward direction along the shaft 14 is generated.

[0051] The powdery chips W are forcibly and smoothly caused to flow in abackward direction by the discharge flow generated and are eventuallydischarged outside the hole part H. At that time, if the shaft 14 isrotated at a peripheral velocity of 250 m/min or greater, preferably of400 m/min, air flow having sufficient speed for discharging the chips Wcan be generated.

[0052] Also, the pressure inside the hole part H becomes negative by thegeneration of the strong discharge flow, and the drilling tool 13 (thehandheld drill 10) is pulled towards the forward direction.

[0053] As explained above, by fixing the bit 15 which drills the drilledmatter C to the tip of the shaft 14 having the spiral groove part 14 aat the outer circumferential surface thereof to form the drilling tool13 and by rotating the drilling tool 13 at a high speed to drill thedrilled matter C, it becomes possible to generate air flow in the holepart H, which is strong enough to discharge the chips W. By adoptingthis configuration, not only use of an air (or water) supply device fordischarging the chips W, which is conventionally required for thedrilled device described above, becomes unnecessary but also it becomespossible to surely and efficiently discharge the chip W even for a deephole of a small diameter which cannot be formed by using a conventionalair supply device as the chips W cannot be discharged.

[0054] That is, it becomes possible to drill a hole by surelydischarging the chips W inside the hole part H which prevents thedrilling operation, it be comes possible to form a deeper hole part H.

[0055]FIG. 3 is a diagram showing another embodiment of the presentinvention. Note that parts that are the same as those shown in FIG. 1are indicated using the same numeral and the explanation thereof isomitted.

[0056] In FIG. 3, the numeral 40 indicates a drilling device which iscapable of drilling a drilled matter by rotating a drilling tool 43. Thedrilling tool 43 has a configuration in which a bit 45 is fixed to thetip of a shaft 44 on which a groove part 44 b is formed, and holes 44 aand 45 a which penetrate in an axial direction are formed in the shaft44 and the bit 45, respectively.

[0057] The drilling tool 40 is fixed to the rotary shaft 41, and holes41 a and 51 a which communicate with the holes 44 a and 45 a, are formedin the rotary shaft 41 and an upper housing 51 which accommodates a rearend portion of the rotary shaft 41 a, respectively. That is, thevicinity of a drilled part of a drilled matter is made to communicatewith the outside by the holes 44 a, 45 a, 41 a, and 51 a. Note that itis not necessary to form the hole 45 of the bit 45 if a notch portionwhich extends to the hole 44 a of the shaft 44 is formed with the bit45.

[0058] When a drilling operation is carried out by rotating the drillingtool 40, a discharge flow is generated along the shaft 44 to dischargechips and an intake flow from the outside to the drilled portion isgenerated via the holes 44 a, 45 a, 41 a, and 51 a, if a spiral groovepart extending in a rear end side with respect to a rear side of therotation direction is formed with the shaft 44. That is, the dischargeflow and the intake flow are separated by the shaft 43 due to thepresence of the holes 44 a and 45 a, and it becomes possible to moresmoothly discharge the chips.

[0059] Also, it is possible to forcibly supply a gas, liquid, mist,etc., to the drilled part using an external device through the holes 44a, 45 a, 41 a, and 51 a. In this manner, not only does a smootherdischarging of chips and drilling operation become possible, but alsothe drilled part of a drilled matter and the bit 45 may be cooled downby supplying water, alcohol, and so on.

[0060] Moreover, an intake flow is generated along the shaft 44 if thegroove part is formed in a spiral shape extending in the rear end sidewith respect to the front side of the rotary direction of the shaft 44,and a discharge flow corresponding to the intake flow is generated fromthe drilled part to the outside through the holes 44 a, 45 a, 41 a, and51 a. Since powdery chips generated at the drilled part are dischargedto the outside through each of the holes by the discharge flow, itbecomes possible to prevent contamination of the work area by the chipsby recovering the chips from the holes. Furthermore, it becomes possibleto readily carry out an operation in which the chips are recovered toconfirm the state of the drilled matter.

[0061] Embodiments:

[0062] As shown in FIGS. 4 and 5, experiments were conducted to comparethe drilling performance of drilling tools according to the presentinvention (one which discharges through the circumference of the shaft)with that of conventional drilling tools (non-core type). The drillingconditions used for the comparison were as follows.

[0063] Drilled matter: plain concrete block

[0064] Drilling type: dry drilling

[0065] Bit diameter: three types (φ6.4 mm, φ10.5 mm, and φ12.7 mm) foreach of the conventional tools and the tools of the present invention

[0066]FIG. 4 is a graph showing the drilling speed of each tool when adrilling operation was carried out using different peripheral velocity.The drilling speed was calculated by measuring the time which wasrequired to make a hole of 50 mm depth by each tool, and indicated bythe distance at which each of the tools could move in a forwarddirection per one minute. Accordingly, as the figures of the drillingspeed becomes larger, the better the performance of the tool.

[0067] From FIG. 4, it is clear that the drilling speed of the presentinvention is faster than the conventional tool of the same diameter inany diameter range, and even a tool of φ12.7 mm diameter of the presentinvention whose drilling speed is the slowest among the tools of theprevent invention can drill at a speed at least equal to that of theconventional tool.

[0068] Also, the reason that the difference between the tools of thepresent invention and the conventional tools becomes larger as the bitdiameter becomes smaller is that it becomes difficult to dischargepowdery chips as the diameter of the hole becomes smaller, and hence thedischarge effect of the present invention using the discharge flowbecomes apparent. As for the hole of 50 mm depth and φ12.7 mm diameter,it is considered that chips were easily removed even when theconventional tool was used.

[0069] Note that the conventional tool of φ6.4 diameter could not drillas the bit thereof fell at the peripheral velocity of 550 m/min. Thereason of this is considered to be the increase in the rotationresistance caused by chips which were not removed from the hole.

[0070]FIG. 5 is a graph showing the differences in the drilling speed atdifferent drilling depths when the tools of present invention and priorart having the bit diameter of φ6.4 mm were used at peripheral velocityof 250 m/min and 500 m/min.

[0071] From FIG. 5, it is clear that the drilling speed wassignificantly reduced in the conventional tool when the drilling depthexceeded 15 mm while no significant change was observed for the tool ofthe present invention, although there was tendency in both tools for thedrilling speed to become slower as the drilling depth increased.

[0072] That is, it becomes difficult to advance the conventional tool aschips are hardly removed from the hole as the depth of the holeincreases while the tool of the present invention can be advanced evenwhen a deep hole is formed because chips are surely removed from thehole regardless of the depth of the hole.

[0073] Note that the shape, combinations, etc., of each structuralmember shown in the above embodiments are mere examples, and variations,and modifications can be made based on design requirements, etc., withinthe scope and sprit of the present invention. For example, only onenotch portion 15 a is formed with the bit 15 (45) in the diagrams;however, it is possible to form two or more of the notch portions inaccordance with the number of the groove parts 14 a of the shaft 14 aslong as it does not decrease the strength of the bit 15, the drillingperformance, and so forth.

[0074] In addition, although the drilling device is a handheld drillwhich a user can hold by hand to perform a drilling operation, it ispossible, of course to provide a base for fixing a drilled matter, andcarry out a drilling operation in a fixed state of the drilled matter.

Industrial Applicability

[0075] As explained above, according to the drilling device of the firstembodiment of the present invention, it becomes possible to readilycarry out a discharging or collecting operation of the chips, asupplying operation of a fluid used for drilling, etc., withoutproviding a special device or mechanism for discharging or collectingthe chips.

[0076] According to the drilling device of the second embodiment of thepresent invention, since powdery chips present in the hole part aredischarged outside of the hole by the discharge flow generated by theshaft rotated at a high-speed, the chips do not remain at a drilledportion to prevent the drilling operation, and a deep hole of smalldiameter, which is difficult to form using a conventional technique, canbe readily formed. Also, since the chips are immediately discharged fromthe drilled portion as the drilling operation proceeds, a special devicewhich supplies a fluid to a drilled portion to discharge the chips or astructure for supplying a fluid to a drilled portion becomesunnecessary, and a simplified and labor saving drilling device may berealized.

[0077] According to the drilling device of the third embodiment of thepresent invention, since air flow is generated along the outer peripheryside of the tool and in the piercing hole so as to flow in the oppositedirections, it becomes possible to more smoothly carry out a dischargingand collecting operation of the chips and a supplying of fluid.

[0078] According to the drilling device of the fourth embodiment of thepresent invention, since air flow is generated along the outer peripheryside of the tool and in the piercing hole so as to flow in the oppositedirections, it becomes possible to readily collect the chips via thepiercing hole without scattering the chips, and a drilling operationwhich does not contaminate the surrounding environment becomes possible.

[0079] According to the drilling tool of the fifth embodiment of thepresent invention, it becomes possible to readily carry out adischarging or collecting operation of the chips, supplying of a fluidfor the drilling operation, etc., by using the air flow generated duringthe drilling operation without using a device or mechanism fordischarging or collecting chips.

[0080] According to the drilling tool of the sixth embodiment of thepresent invention, since the powdery chips present in the hole may bedischarged outside as the drilling operation proceeds, and hence thechips do not remain at a drilled portion to prevent the drillingoperation, a deep hole of small diameter, which is difficult to formusing a conventional technique, can be readily formed.

[0081] According to the drilling tool of the seventh embodiment of thepresent invention, since air flow which flows along the outer peripheryof the tool and air flow which flows through the piercing hole aregenerated so as to flow in the opposite directions, it becomes possibleto perform a drilling operation while smoothly generating the dischargeand intake flows.

[0082] According to the drilling tool of the eighth embodiment of thepresent invention, since air flow which flows along the outer peripheryof the tool and air flow which flows through the piercing hole aregenerated so as to smoothly flow in the opposite directions, it becomespossible to readily collect the chips through the piercing hole withoutscattering the chips, and hence, a drilling operation may be carried outWithout contaminating the operating environment.

[0083] According to the drilling method of the ninth embodiment of thepresent invention, it becomes possible, for example, to readilydischarge the powdery chips to the outside of the hole part, and tosupply liquid, such as water, to the drilling portion from the outsideof the hole by using the air flow which is generated in association withthe drilling operation.

[0084] According to the drilling method of the tenth embodiment of thepresent invention, it becomes possible to readily discharge the chips tothe outside of the hole from the drilling portion by using the dischargeflow which is generated during the drilling operation. Accordingly, itbecomes possible to prevent the chips to remain at the drilling portion,which may make the drilling operation impossible, and to readily form adeep hole of small diameter.

[0085] According to the drilling method of the eleventh embodiment ofthe present invention, since each of the air flow which is separated bythe drilling tool is smoothly flows in the opposite directions at theinner periphery side and the inner periphery side of the drilling toolhaving the piercing hole, it becomes possible to smoothly form a deephole of small diameter.

[0086] According to the drilling method of the twelfth embodiment of thepresent invention, since the chips can be discharged to the outside ofthe drilled matter from the drilling portion via the piercing holethrough which the discharge flow flows, it becomes possible, forexample, to collect the chips without scattering them by connecting ameans for collecting the chips to the piercing hole.

1. A drilling device for forming a hole in a brittle drilled matter fromwhich powdery chips are generated, comprising: a tool which includes ashaft and a disc shape bit fixed to an end portion of said shaft; and arotation driving device which rotates and drives said tool, wherein aspiral groove part which extends to a tip of said bit is formed in anouter peripheral surface of said shaft of said tool, and said tool isrotated at a revolution number peripheral velocity of 250 m/min or moreby said rotation driving device.
 2. A drilling device according to claim1, wherein said spiral groove part is provided so as to generate airflow from a tip side of said shaft to a rear end side along said groovepart by the rotation of said tool due to obliquity of said spiral groovepart extending towards a rear side of a rotation direction by saidrotation driving device and towards a rear end side of said shaft.
 3. Adrilling device according to claim 1, wherein a hole which penetratesthough said shaft to reach the tip of said bit is formed in said tool sothat a vicinity of said bit communicates with air present at a rear endside of said shaft.
 4. A drilling device according to claim 1, whereinsaid spiral groove part is provided so as to generate air flow from arear end of said tool to a tip side of said shaft along said groove partby the rotation of said tool due to obliquity of said spiral groove partextending towards a rear side of a rotation direction by said rotationdriving device and towards a tip side of said shaft, and a hole whichpenetrates though said shaft to reach the tip of said bit is formed insaid tool so that the tip side of said bit communicates with air presentat a rear end side of said shaft.
 5. A drilling tool, comprising: ashaft and a disc shape bit fixed to an end portion of said shaft,wherein a spiral groove part which extends to a tip of said bit isformed in an outer peripheral surface of said shaft, and said tool isrotated at a revolution peripheral velocity of 250 m/min or more to forma hole in a brittle drilled matter from which powdery chips aregenerated.
 6. A drilling tool according to claim 5, wherein said spiralgroove part is provided so as to generate air flow from a tip side ofsaid shaft to a rear end side along said groove part by the rotation ofsaid tool due to obliquity of said spiral groove part extending towardsa rear side of a rotation direction and towards a rear end side of saidshaft.
 7. A drilling tool according to claim 5, wherein a hole whichpenetrates though said shaft to reach the tip of said bit is formed sothat a vicinity of said bit communicates with air present at a rear endside of said shaft.
 8. A drilling tool according to claim 5, whereinsaid spiral groove part is provided so as to generate air flow from arear end of said shaft to a tip side of said shaft along said groovepart by the rotation of said tool due to obliquity of said spiral groovepart extending towards a rear side of a rotation direction and towards atip side of said shaft, and a hole which penetrates though said shaft toreach the tip of said bit is formed so that a vicinity of the bitcommunicates with air present at a rear end side of said shaft.
 9. Amethod for drilling a hole in a brittle drilled matter from whichpowdery chips are generated by rotating and driving a drilling tool inwhich a bit is fixed to a tip of a shaft, said method comprising thestep of: performing a drilling process while generating air flow whichflows from a vicinity of said bit to air present at a rear end side ofsaid shaft by utilizing a rotation of said drilling tool.
 10. A methodfor drilling according to claim 9, wherein said air flow generated byutilizing the rotation of said drilling tool is a discharge flow whichflows from a tip side to a rear end side along an outside of saiddrilling tool.
 11. A method for drilling according to claim 9, furthercomprising the step of: generating another air flow which flows in anopposite direction of said air flow generated by the rotation of saiddrilling tool, so as to flow through a hole which penetrates through atip side to a rear end side of said drilling tool.
 12. A method fordrilling according to claim 9, wherein said air flow generated byutilizing the rotation of said drilling tool is an intake flow whichflows from a tip side to a rear end side along an outside of saiddrilling tool, and further comprising the step of: generating anotherair flow which flows an opposite direction of said intake flow so as toflow through a hole which penetrates through a tip side to a rear endside of said drilling tool.